Allen&Heath GL4000 SERVICE MANUAL - Manual (Page 42)

Publication AP2787
SYS-LINK APPLICATIONS NOTE
GL4000
MIXING CONSOLE
For information on fitting SYS-LINK please refer to FITTING INSTRUCTIONS AP2786
THE BENEFITS OF USING SYS-LINK
The GL4000 SYS-LINK option allows console to console interconnection by means of just one
or two cables. By connecting two GL4000 consoles together the number of input channels may
be increased. One console acts as a channel expander (slave) to the second (master). Up to 3
consoles may be 'daisy-chained' in this way. The system is also directly compatible with other
A&H consoles fitted with SYS-LINK.
Plugging consoles together using SYS-LINK connects the signals directly to the console busses
so avoiding the use of the main console outputs and channel inputs for the master / slave
connection. All the console channels are available to the user for input sources.
SYS-LINK CONNECTIONS
SYS-LINK connects all the console main busses including L, R, Mono, 8 Groups, 10 Aux sends,
and 4 matrices. The PFL & AFL systems are also interconnected such that operating PFL or
AFL on the slave console activates the master console monitor system. Operating PFL or AFL
on the master does not activate the slave monitor system which may be used for 'local'
monitoring if required. SYS-LINK connects the PFL & AFL audio mix and DC control buss.
SYS-LINK outputs are taken pre-fader so that the slave console output connectors may be used
for sub-mix or 'zone' feeds if required. All output signals are unbalanced, low impedance and
operate at a line level of -2dBu to prevent problems with audio interference and to maintain a
headroom of 23dB.
SYS-LINK inputs are unbalanced, operate line level at -2dBu and are high impedance to prevent
loading the connected source.
SYS-LINK is presented on two pairs of 25way female D-type connectors, one for the console
buss inputs and the other for the outputs. Several pins are provided for audio 0V earth.
USING SYS-LINK
Connect consoles using two standard 25way male to male D-type cables, available from
electronic suppliers or computer shops (25line male to male). It is advised that this cable is a
screened type if longer than 1 metre, no longer than 10 metres in total, and that professional
quality locking connectors are used. Connect all pins one to one with the screen to 0V.
Connect the slave console SYS-LINK output to the master console SYS-LINK input.
SYS-LINK may also be used to connect the GL4000 to other audio equipment. Make sure that
all unused inputs (except the PFL & AFL DC inputs) are linked to 0V earth at the SYS-LINK
input to prevent audible interference from connected audio signals. Connect line level signals
of around -2dBu. The GL4000 PFL & AFL systems may be activated by switching the PFL or
AFL DC inputs to 0V earth through a 15k ohm resistor.
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Issue 2 July 01